Demodulation for phase-noise mitigation in 5G and 6G

ABSTRACT

At high frequencies planned for 5G and 6G, phase noise may be a limiting factor on reliability and throughput. The default modulation scheme is currently QAM. Disclosed is a more versatile demodulation method based on the amplitude and phase of the sum-signal, which is the vector sum of the two branch amplitudes of QAM. The transmitter modulates a message by sum-signal amplitude and phase. The receiver can process the received waveform according to quadrature branches as usual, and determines the branch amplitudes. The receiver then calculates, from the branch amplitudes, the sum-signal amplitude and sum-signal phase for demodulation. The receiver can thereby obtain substantially enhanced phase-noise tolerance and amplitude spacing uniformity at virtually no cost. In addition, methods are disclosed for determining specific message fault types and non-square modulation tables depending on the type of mitigation required. Sum-signal modulation can provide access to high-frequency bands with enhanced reliability and throughput.

PRIORITY CLAIMS AND RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 63/418,784, entitled “Demodulation for Phase-NoiseMitigation in 5G and 6G”, filed Oct. 24, 2022, and U.S. ProvisionalPatent Application Ser. No. 63/412,654, entitled “Guard-SpacePhase-Tracking Reference Signal for 5G and 6G Networking”, filed Oct. 3,2022, and U.S. Provisional Patent Application Ser. No. 63/403,924,entitled “Phase-Noise Mitigation at High Frequencies in 5G and 6G”,filed Sep. 6, 2022, and U.S. Provisional Patent Application Ser. No.63/409,888, entitled “Single-Branch Reference for High-Frequency PhaseTracking in 5G and 6G”, filed Sep. 26, 2022, and U.S. Provisional PatentApplication Ser. No. 63/321,879, entitled “Low-Complexity Demodulationof 5G and 6G Messages”, filed Mar. 21, 2022, and U.S. Provisional PatentApplication Ser. No. 63/309,748, entitled “Error Detection andCorrection in 5G/6G Pulse-Amplitude Modulation”, filed Feb. 14, 2022,and U.S. Provisional Patent Application Ser. No. 63/280,281, entitled“Error Detection and Correction by Modulation Quality in 5G/6G”, filedNov. 17, 2021, all of which are hereby incorporated by reference intheir entireties.

FIELD OF THE INVENTION

The disclosure pertains to phase-noise mitigation in wireless messaging,and particularly to phase-noise mitigation at high frequencies.

BACKGROUND OF THE INVENTION

Wireless communication at very high frequencies, such as tens tohundreds of GHz, is needed for the massively increased demand inbandwidth and throughput expected in 5G and 6G. However, phase noise isan increasing problem at higher frequencies, preventing full usage ofthe bandwidth for messaging. What is needed is means for mitigating thephase noise so that the promise of high-speed messaging at highfrequencies can be at least partially realized.

This Background is provided to introduce a brief context for the Summaryand Detailed Description that follow. This Background is not intended tobe an aid in determining the scope of the claimed subject matter nor beviewed as limiting the claimed subject matter to implementations thatsolve any or all of the disadvantages or problems presented above.

SUMMARY OF THE INVENTION

In a first aspect, there is a method for a wireless receiver todemodulate a message, the method comprising: receiving a messagecomprising message elements, each message element modulated according toa modulation scheme, the modulation scheme comprising amplitudemodulation multiplexed with phase modulation, the amplitude modulationaccording to a first plurality of predetermined amplitude levels, andthe phase modulation according to a second plurality of predeterminedphase levels; for each message element, determining a message I-branchsignal multiplexed with an orthogonal message Q-branch signal, anddetermining a message I-branch amplitude of the message I-branch signal,and determining a message Q-branch amplitude of the message Q-branchsignal; for each message element, calculating, according to the messageI-branch amplitude and the message Q-branch amplitude, a messagesum-signal amplitude and a message sum-signal phase; and for eachmessage element, selecting a closest amplitude level, of the firstplurality of predetermined amplitude levels, to the message sum-signalamplitude, and selecting a closest phase level, of the second pluralityof predetermined phase levels, to the message sum-signal phase.

In another aspect, there is non-transitory computer-readable media in awireless receiver, the media containing instructions that whenimplemented in a computing environment cause a method to be performed,the method comprising: receiving a first message comprising messageelements, wherein each message element is amplitude modulated and phasemodulated according to a first modulation scheme; determining, accordingto an error-detection code associated with the first message, that thefirst message is corrupted; receiving a second message, and determining,according to a second error-detection code associated with the secondmessage, that the second message is not corrupted; determining, for eachmessage element of the first and second messages, a raw-signal amplitudeand a raw-signal phase; for each message element, comparing theraw-signal amplitudes of the first and second messages, and comparingthe raw-signal phases of the first and second messages; and determining,according to the comparing, which message elements of the first messageare faulted.

In another aspect, there is a receiver in a wireless network, thereceiver configured to: receive a particular message element of awireless message, the particular message element comprising a rawsignal, the raw signal modulated according to a modulation scheme, themodulation scheme comprising amplitude modulation multiplexed with phasemodulation; separate the raw signal into an I-branch signal and anorthogonal Q-branch signal; measure an I-branch amplitude of theI-branch signal and a Q-branch amplitude of the Q-branch signal;calculate, according to the I-branch amplitude and the Q-branchamplitude, a received sum-signal amplitude and a received sum-signalphase; and demodulate the particular message element according to thereceived sum-signal amplitude and the received sum-signal phase.

This Summary is provided to introduce a selection of concepts in asimplified form. The concepts are further described in the DetailedDescription section. Elements or steps other than those described inthis Summary are possible, and no element or step is necessarilyrequired. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended foruse as an aid in determining the scope of the claimed subject matter.The claimed subject matter is not limited to implementations that solveany or all disadvantages noted in any part of this disclosure.

These and other embodiments are described in further detail withreference to the figures and accompanying detailed description asprovided below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic showing an exemplary embodiment of a 16QAMconstellation chart, according to some embodiments.

FIG. 1B is a schematic showing an exemplary embodiment of the effect ofphase noise on a 16QAM constellation chart, according to someembodiments.

FIG. 2A is a polar plot showing an exemplary embodiment of sum-signalamplitudes and phases in 16QAM, according to some embodiments.

FIG. 2B is a schematic showing an exemplary embodiment of aconstellation chart with states shaded to indicate the sum-signalamplitude, according to some embodiments.

FIG. 3A is a sketch showing an exemplary embodiment of waveforms of QAMbranches and a sum-signal, according to some embodiments.

FIG. 3B is a constellation chart showing an exemplary embodiment of QAMand sum-signal parameters, according to some embodiments.

FIG. 3C is a chart showing an exemplary embodiment of a sum-signalmodulation table, according to some embodiments.

FIG. 3D is a chart showing an exemplary embodiment of the sum-signalamplitudes and phases of 16QAM states, according to some embodiments.

FIG. 4 is an flowchart showing an exemplary embodiment of a method toreceive a message using quadrature components, and demodulate themessage using the sum-signal amplitude and phase, according to someembodiments.

FIG. 5A is an exemplary embodiment of a sum-signal modulation table,according to some embodiments.

FIG. 5B is an exemplary embodiment of a sum-signal modulation tableincluding phase noise, according to some embodiments.

FIG. 5C is an exemplary embodiment of a sum-signal modulation tableincluding amplitude noise, according to some embodiments.

FIG. 5D is a flowchart showing an exemplary embodiment of a method tomitigate amplitude noise and phase noise in sum-signals, according tosome embodiments.

FIG. 6 is a flowchart showing an exemplary embodiment of a procedure fortransmitting and receiving a message and using sum-signal demodulationto mitigate amplitude noise and phase noise, according to someembodiments.

FIG. 7A is an exemplary embodiment of a sum-signal modulation tableincluding various types of faults, according to some embodiments.

FIG. 7B is a flowchart showing an exemplary embodiment of a method toselect a modulation table to mitigate various types of faults, accordingto some embodiments.

FIG. 8 is an exemplary embodiment of a sum-signal modulation tableconfigured to mitigate phase faults, according to some embodiments.

FIG. 9 is a schematic showing an exemplary embodiment of a message withvarious types of faults, according to some embodiments.

FIG. 10 is a schematic showing an exemplary embodiment of a method toselect a modulation table based on types of faults observed, accordingto some embodiments.

Like reference numerals refer to like elements throughout.

DETAILED DESCRIPTION

Systems and methods disclosed herein (the “systems” and “methods”, alsooccasionally termed “embodiments” or “arrangements” or “versions” or“examples”, generally according to present principles) can provideurgently needed wireless communication protocols for mitigating theeffects of phase noise at high frequencies planned for late 5G and 6Gcommunications. Disclosed herein is a “sum-signal demodulation method”to demodulate a message with enhanced noise margin for phase noise and,in some cases, for amplitude noise as well, according to someembodiments. The sum-signal of a message element is the vector sum oftwo orthogonal branch amplitudes, and represents the overall amplitudeand phase of the received waveform. Examples show how the sum-signal isrelated to the branch signals of QAM. Further examples demonstrateadvantages in correcting for phase noise and, separately, for amplitudenoise, using sum-signal techniques. Further examples show how todiagnose message faults according to sum-signal amplitude and phasedeviations, and how to select a different modulation table to combatvarious types of faults. In summary, to achieve enhanced noise margins:(a) a transmitter modulates the amplitude and phase of the overallwaveform of a message element, and transmits it; (b) a receiver receivesthe waveform and extracts orthogonal I and Q branch signals; (c) thereceiver measures the I and Q branch amplitudes, and calculates theresultant sum-signal amplitude and phase; (d) the message is thendemodulated using predetermined sum-signal amplitude and phase levels.

The examples presented below are suitable for adoption by a wirelessstandards organization. Providing a sum-signal modulation option withenhanced phase-noise tolerance, as a standard, may enable high-frequencyoperation with enhanced reliability, at zero or negligible cost in powerand resources, greatly benefitting future 5G/6G wireless usersworldwide.

Terms herein generally follow 3GPP (third generation partnershipproject) standards, but with clarification where needed to resolveambiguities. As used herein, “5G” represents fifth-generation, and “6G”sixth-generation, wireless technology in which a network (or cell or LANLocal Area Network or RAN Radio Access Network or the like) may includea base station (or gNB or generation-node-B or eNB or evolution-node-Bor AP Access Point) in signal communication with a plurality of userdevices (or UE or User Equipment or user nodes or terminals or wirelesstransmit-receive units) and operationally connected to a core network(CN) which handles non-radio tasks, such as administration, and isusually connected to a larger network such as the Internet. Thetime-frequency space is generally configured as a “resource grid”including a number of “resource elements”, each resource element being aspecific unit of time termed a “symbol period” or “symbol-time”, and aspecific frequency and bandwidth termed a “subcarrier” (or “subchannel”in some references). Symbol periods may be termed “OFDM symbols”(Orthogonal Frequency-Division Multiplexing) in references. The timedomain may be divided into ten-millisecond frames, one-millisecondsubframes, and some number of slots, each slot including 14 symbolperiods. The number of slots per subframe ranges from 1 to 8 dependingon the “numerology” selected. The frequency axis is divided into“resource blocks” (also termed “resource element groups” or “REG” or“channels” in references) including 12 subcarriers, each subcarrier at aslightly different frequency. The “numerology” of a resource gridcorresponds to the subcarrier spacing in the frequency domain.Subcarrier spacings of 15, 30, 60, 120, and 240 kHz are defined invarious numerologies. Each subcarrier can be independently modulated toconvey message information. Thus a resource element, spanning a singlesymbol period in time and a single subcarrier in frequency, is thesmallest unit of a message. “Classical” amplitude-phase modulationrefers to message elements modulated in both amplitude and phase,whereas “quadrature” or “PAM” (pulse-amplitude) modulation refers to twosignals, separately amplitude-modulated, and then multiplexed andtransmitted with a 90-degree phase shift between them. The two signalsmay be called the “I” and “Q” branch signals (for In-phase andQuadrature-phase) or “real and imaginary” among others. Standardmodulation schemes in 5G and 6G include BPSK (binary phase-shiftkeying), QPSK (quad phase-shift keying), 16QAM (quadrature amplitudemodulation with 16 modulation states), 64QAM, 256QAM and higher orders.Most of the examples below relate to QPSK or 16QAM, with straightforwardextension to the other levels of modulation. QPSK is phase modulated butnot amplitude modulated. 16QAM may be modulated according to PAM whichexhibits two phase levels at zero and 90 degrees (or in practice, forcarrier suppression, ±45 degrees) and four amplitude levels includingtwo positive and two negative amplitude levels, thus forming 16 distinctmodulation states. For comparison, classical amplitude-phase modulationwith 16 states includes four positive amplitude levels and four phasesof the raw signal, which are multiplexed to produce the 16 states of themodulation scheme. “SNR” (signal-to-noise ratio) and “SINR”(signal-to-interference-and-noise ratio) are used interchangeably unlessspecifically indicated. “RRC” (radio resource control) is a control-typemessage from a base station to a user device. “Digitization” refers torepeatedly measuring a waveform using, for example, a fast ADC(analog-to-digital converter) or the like. An “RF mixer” is a device formultiplying an incoming signal with a local oscillator signal, therebyselecting one component of the incoming signal.

In addition to the 3GPP terms, the following terms are defined herein.Although in references a modulated resource element of a message may bereferred to as a “symbol”, this may be confused with the same term for atime interval (“symbol-time”), among other things. Therefore, eachmodulated resource element of a message is referred to as a “modulatedmessage resource element”, or more simply as a “message element”, inexamples below. A “demodulation reference” is a set of Nref modulated“reference resource elements” or “reference elements” modulatedaccording to the modulation scheme of the message and configured toexhibit levels of the modulation scheme (as opposed to conveying data).Thus integer Nref is the number of reference resource elements in thedemodulation reference. A “calibration set” is one or more amplitudevalues and/or phase values, which have been determined according to ademodulation reference, representing the predetermined modulation levelsof a modulation scheme. A “short-form” demodulation reference is ademodulation reference that exhibits the maximum and minimum amplitudelevels of the modulation scheme, from which the receiver can determineany intermediate levels by interpolation. “RF” or radio-frequency refersto electromagnetic waves in the MHz (megahertz) or GHz (gigahertz)frequency ranges. The “raw” signal is the as-received waveform beforeseparation of the quadrature branch signals. “Phase noise” is randomnoise or time jitter that alters the phase of a received waveform,usually without significantly affecting the overall amplitude.“Phase-noise tolerance” is a measure of how much phase alteration can beimposed on a message element without causing a demodulation fault.“Amplitude noise” includes any noise or interference that primarilyaffects the amplitude of a received waveform. Interference due tocompeting signals is treated as noise herein, unless otherwisespecified. A “faulted” message has at least one incorrectly demodulatedmessage element. A “phase fault” is a message element demodulated as astate differing in phase from the intended modulation state, whereas an“amplitude fault” is a message element demodulated as a state differingin amplitude from the intended modulation state.

Referring to quadrature or PAM or QAM modulation, an “I-Q” space is anabstract two-dimensional space defined by an I-branch amplitude and anorthogonal Q-branch amplitude, in which each transmitted message elementoccupies one of several predetermined I-Q states of a modulation scheme.When the orthogonal branches are called “real” and “imaginary”, the I-Qspace is sometimes called the “complex plane”. The receiver may processthe received signals by determining a “sum-signal”, which is the vectorsum of the I and Q branch signals. A vector sum is a sum of two vectors,which in this case represent the amplitudes and phases of the twoorthogonal branches in I-Q space. The sum-signal has a “sum-signalamplitude”, equal to the square root of the sum of the I and Q branchamplitudes squared (the “root-sum-square” of I and Q), and a “sum-signalphase”, equal to the arctangent of the ratio of the I and Q signalamplitudes (plus an optional base phase, ignored herein). Thus thesum-signal represents the raw received waveform, aside from signalprocessing errors which are generally negligible and are ignored herein.

When the message element is received at a receiver, the I and Qamplitudes may be substantially different from the transmitted valuesdue to phase noise and amplitude noise, which distort the I and Qamplitudes in complex ways. The sum-signal, on the other hand, isgenerally affected by amplitude noise and phase noise separately, and ina direct way. Hence, modulating according to the sum-signal amplitudeand sum-signal phase enables effective mitigation of both amplitudenoise and phase noise, whereas modulating according to QAM branches doesnot. (This assumes the amplitude noise and phase noise affect themessage element in the same was as a proximate demodulation reference,as disclosed below.) In addition, sum-signal demodulation enables faultdiagnostics which reveal the sources of message faults. In addition,sum-signal modulation can combat particular types of noise usingnon-square or asymmetric modulation tables, which QAM cannot.

Most of the examples are presented using 16QAM and the corresponding16-state sum-signal amplitude-phase modulation states; however, theprinciples apply equally to higher-order modulation schemes withstraightforward modifications.

Turning now to the figures, a prior-art modulation scheme is susceptibleto phase noise at high frequencies.

FIG. 1A is a schematic showing an exemplary embodiment of a 16QAMconstellation chart, according to some embodiments. As depicted in thisnon-limiting example, a modulation scheme 101 includes 16 allowedmodulation states 102, each allowed state determined by an I-branchsignal and a Q-branch signal orthogonal to the I-branch signal (forexample, the Q-branch phase-modulated at 90 degrees relative to theI-branch). The horizontal axis shows the amplitude modulation of theI-branch signal, and the vertical axis shows the amplitude modulation ofthe Q-branch signal, each branch being amplitude-modulated at one ofcertain predetermined branch amplitude levels of the modulation scheme.In this case, the predetermined branch amplitude levels are −3, −1, +1,and +3 arbitrary units. For example, the distance 103 may be 1 unit, andthe distance 104 may be 3 units. The various branch amplitude levels areequally separated and symmetrical around zero. The central cross-shaperepresents zero branch amplitude. Negative branch amplitude levels areequivalent to a 180-degree phase change of the branch. There are 16states, as expected for 16QAM. A receiver can receive a message elementmodulated according to this modulation scheme, and can extract the I andQ branches separately by analog or digital signal-processing means. Thereceiver can then measure the branch amplitudes of those two branches,compare the measured branch amplitude values to a predetermined set ofbranch amplitude levels, select the closest match to each branchamplitude, and thereby determine the modulation state of the messageelement. 16QAM encodes 4 bits per message element.

Also shown are the corresponding sum-signal amplitude 105 and sum-signalphase 106 of a particular state 107. The sum-signal amplitude 105 is theradius of the state 107 from the origin, and the sum-signal phase 106 isthe angle relative to the horizontal axis (ignoring carrier suppression,etc.). Thus each state 102 can be described in terms of the I and Qbranch amplitudes, or by the sum-signal amplitude and phase.

FIG. 1B is a schematic showing an exemplary embodiment of the effect ofphase noise on a 16QAM constellation chart, according to someembodiments. As depicted in this non-limiting example, the modulationstates 112 of a 16QAM constellation chart 111 can be distorted (“smearedout”) by phase noise in a characteristic way as indicated by phasedistortion clouds 118. The depicted distortions would be caused bymoderate phase noise at moderate frequencies; at high frequencies it ismuch worse. If the same modulation scheme were attempted at the muchhigher frequencies planned for future wireless operation, the increasedphase noise would cause the phase-noise clouds to overlap, resulting infrequent message faults. Hence the need for strategies to enablecommunication despite strong phase distortions.

Also shown are arrows qualitatively indicating the effects of noise. Anarc arrow 116 shows how phase noise alters the I and Q branchamplitudes. A particular pair of 16QAM states, indicated by arrow 113,are separated by only 37 degrees of phase. Such pairs of states, thatsit relatively close together in phase, determine the limiting phasenoise tolerance of 16QAM, because a relatively small phase rotationangle can cause those two states to mimic each other, causing messagefaults.

FIG. 2A is a polar plot showing an exemplary embodiment of sum-signalamplitudes and phases in 16QAM, according to some embodiments. Asdepicted in this non-limiting example, the states of 16QAM are shadedaccording to the corresponding sum-signal amplitude. The lowestsum-signal amplitude is shown as a circle 203 and the four states withthat sum-signal amplitude are shown as dark gray dots 204. The fourstates with the largest sum-signal amplitude are shown as white dots 206on the large circle 201. The eight states with the intermediatesum-signal amplitude are shown light gray 205 on the middle circle 202.It is noteworthy that all eight intermediate states have the samesum-signal amplitude, and therefore differ only in their phase.

Also shown is an arrow 208 indicating the sum-signal amplitude of aparticular state 207, and an arc 209 indicating the sum-signal phase ofthe state 207.

The I and Q branch amplitudes are related to the sum-signal phase andamplitude according to mathematical formulas. The sum-signal amplitude208 equals the square root of the sum of the squares of the I and Qbranch amplitudes (that is, the “root-sum-square” of I and Q), while thesum-signal phase 209 equals the arctangent of the Q branch amplitudedivided by the I branch amplitude. Likewise, the I branch amplitudeequals the sum-signal amplitude 208 times the cosine of the sum-signalphase 209, and the Q branch amplitude equals the sum-signal amplitude208 times the sine of the sum-signal phase 209. Conversion between thequadrature parameters and the sum-signal parameters is thusstraightforward.

Although the branch amplitudes are modulated with four branch amplitudelevels in 16QAM, the actual transmitted waveform has only three distinctamplitudes, as shown by the three circles 201, 202, 203. This is becauseeight of the 16QAM states have the same overall amplitude, which in theexample is 3.16 arbitrary units (that is, √(3²+1²) in this case). Thethree amplitude values of the transmitted waveforms are not equallyspaced, as shown by the three circles 201, 202, 203 havingnon-equally-spaced radii (specifically 1.41, 3.16, and 4.24 arbitraryunits in this case). Thus, although the branch amplitudes are modulatedaccording to four amplitude levels, the transmitted and received wavehas only three distinct amplitude levels, in 16QAM. The unequal spacingof the overall waveform amplitudes can limit the amplitude noiseimmunity, as described below.

FIG. 2B is a schematic showing an exemplary embodiment of aconstellation chart with states shaded to indicate the sum-signalamplitude, according to some embodiments. As depicted in thisnon-limiting example, the modulation states of 16QAM are again depictedas a constellation table, with the I-branch amplitude horizontally andthe Q-branch amplitude vertically. The scales are in arbitrary units.The states are shaded in the same way as the dots of FIG. 2A, white forthe largest-amplitude sum-signal states 216, light gray for theintermediate states 215, and dark gray for the smallest sum-signalamplitudes 214. Also shown is a phase separation 213 between two of thestates, which corresponds to the same dimension 113 between the same twostates in FIG. 1B. As mentioned, the phase separation is only 37degrees, which limits the phase noise tolerance in 16QAM and similarmodulation schemes.

FIG. 3A is a sketch showing an exemplary embodiment of waveforms of QAMbranches and a sum-signal, according to some embodiments. As depicted inthis non-limiting example, the waveform of an I-branch signal 301 and aQ-branch signal 302 are shown versus phase (or equivalently, versustime). Also shown is the sum-signal 303 formed by adding the two branchamplitudes 301, 302 together. The sum-signal 303 is the waveform that isactually transmitted by a transmitter and received by the antenna of areceiver, before separation of the branches 301, 302 by electronics. Thetransmitter does not transmit the I and Q branches 301, 302 explicitly;it transmits the sum-signal 303. The sum-signal 303 has a (zero-to-peak)amplitude 306 and a (crest) phase 307 as shown. When a receiverseparates the two branch signals, the I-branch amplitude is equivalentto the sum-signal value at a phase of zero, as indicated by a first box304 where the Q-branch signal passes through zero. Likewise the Q-branchamplitude is equivalent to the sum-signal value at 90 degrees asindicated by a second box 305, which is where the I-branch waveformpasses through zero. In this case, the boxes 304, 305 indicate that theI-branch amplitude is positive and the Q-branch amplitude is negative,as indicated by the boxes 304, 305 being positive and negative inamplitude. Accordingly, the I-branch waveform 301 shows a maximallypositive value at zero degrees, while the Q-branch waveform 302 shows amaximally negative value at 90 degrees. The sum-signal 303 is the sum ofthe branch waveforms 301, 302 and the sum-signal amplitude and phase306, 307 are related by trigonometric formulas to the I and Q branchamplitudes, as mentioned. In this specific case, the sum-signalamplitude 306 is √2 times the amplitude of the I and Q branches 301, 302and the sum-signal phase 307 is 315 degrees as shown.

FIG. 3B is a constellation chart showing an exemplary embodiment of16QAM and the corresponding sum-signal parameters, according to someembodiments. As depicted in this non-limiting example, the modulationstates 310 of 16QAM are shown as dots versus the I and Q branchamplitudes, with zero amplitude at the center. A particular state 319 isshown with a sum-signal amplitude 312 and a sum-signal phase 311 asindicated by arrows. That state 319 has the maximally positive Iamplitude, maximally negative Q amplitude, and a sum-signal phase of 315degrees. This state 319 corresponds to the sum-signal waveform 303, ofFIG. 3A.

FIG. 3C is an exemplary embodiment of a sum-signal modulation table,according to some embodiments. As depicted in this non-limiting example,little circles 320 represent the modulation states of a sum-signalamplitude-phase modulation scheme with 16 states. Although the layoutappears similar to the constellation chart of 16QAM, the meaning isquite different. The modulation table of FIG. 3C shows the sum-signalphase on the horizontal axis and the sum-signal amplitude vertically.The sum-signal amplitude levels are equally spaced at 1 unit, and thesum-signal phase levels are equally-spaced by 90 degrees. Since phase isa circular parameter, the phase separation between the first and lastcolumn is also 90 degrees, although this type of chart does not makethat obvious.

There are 16 states with sum-signal amplitude and phase modulation,thereby encoding 4 bits per message element. Hence, messages are thesame length whether modulated in 16QAM or sum-signal amplitude-phasemodulation. The difference between these modulation schemes, however, isin noise sensitivity. For example, the phase separation betweensum-signal states is a uniform 90 degrees, whereas the closest 16QAMphase separation is 37 degrees. In addition, the four sum-signalamplitude levels are equally spaced apart, whereas the three overallamplitude levels of 16QAM are not equally spaced, as mentioned.

FIG. 3D is a chart showing an exemplary embodiment of the sum-signalamplitudes and phases of 16QAM states, according to some embodiments. Asdepicted in this non-limiting example, the states of 16QAM are shownplotted against the sum-signal amplitude and sum-signal phase of eachstate. When a message element is modulated in 16QAM, the actualtransmitted waveform has the overall amplitude and phase values shown inthis chart, and the receiver receives the overall waveform with theseamplitude and phase values (absent noise) before the I and Q branchesare extracted.

The sum-signal states with the largest amplitude are shown as four whitesquares 336, corresponding to the “corner” squares in a QAMconstellation chart, such as the white squares 216 in FIG. 2B or thewhite dots 206 in FIG. 2A. The four dark squares 334 are the smallestamplitude states, corresponding to the dark squares and circles 204 and214 in FIGS. 2A and 2B. The eight gray squares 335 are theintermediate-amplitude states corresponding to the gray states 215 and225 in FIGS. 2A and 2B. A particular state 339 has the highestsum-signal amplitude and a sum-signal phase of 45 degrees, and thuscorresponds to the state 310 in FIG. 3B. Likewise, the state 336 in thischart corresponds to 319 in FIG. 3B, and to 303 in FIG. 3A.

Also shown is a phase separation 333 between two of theintermediate-amplitude states 335. This phase separation 333 correspondsto the same dimension labeled as 213 in FIG. 2B. As can be seen in thechart, the intermediate-amplitude states 335 of 16QAM are clusteredtogether in pairs, separated by only 37 degrees of phase. In addition,the amplitude separations are unequal (corresponding to 1.08 and 2.02arbitrary units in this case). The problem is that at high frequencies,the phase noise tends to dominate over amplitude noise, and thereforethe phase clustering of QAM states leads to excessive phase noisefaulting. At high frequencies, the clustering of QAM states in phase,and spreading in amplitude, is the exact opposite of what may be desiredfor reliable messaging at high frequencies. Instead, a better modulationscheme for high frequencies may have equal large phase separationbetween states for phase-noise immunity, and additional amplitude levelsfor high throughput.

For example, FIG. 3C shows that the sum-signal modulation scheme has thedesired properties. The sum-signal phase levels are all separated by afull 90 degrees as desired, thereby providing over 2.4 times largerphase noise tolerance than 16QAM. In addition, there are four sum-signalamplitude levels instead of three overall amplitudes of 16QAM, and theyare equally spaced when modulated according to the sum-signal amplitudeand phase instead of modulating by branch amplitudes. Noise attacks theoverall received waveform, not the individual branches, and hence theclose phase separation between adjoining states in 16QAM leads tounwanted phase faults. For these reasons, the sum-signal modulationscheme may be better suited to high-frequency messaging than QAM,especially when high throughput is needed and phase noise is limiting.

FIG. 4 is an flowchart showing an exemplary embodiment of a method toreceive a message using quadrature components, and demodulate themessage using the sum-signal amplitude and phase, according to someembodiments. As depicted in this non-limiting example, a message ismodulated, by the transmitter, in equally-spaced sum-signal amplitudesand phases, but is processed as quadrature branch signals by thereceiver. The receiver then calculates the received sum-signal amplitudeand phase, and demodulates the message according to predeterminedsum-signal amplitude levels and sum-signal phase levels. This method canprovide improved phase noise tolerance because the phase separation ofthe sum-signal states is larger than the phase separation of thequadrature-modulated states.

At 401, a transmitter modulates a message element of a message accordingto predetermined sum-signal amplitude levels and sum-signal phase levelsof a sum-signal modulation scheme such as that of FIG. 3C. Thetransmitter then transmits the message element as a sinusoidal waveformhaving the sum-signal amplitude and the sum-signal phase. At 402, thereceiver receives the waveform and separates the two orthogonal I and Qcomponents or branches. The receiver then processes (amplifies, filters,digitizes, etc.) the I and Q branch signals, and then measures the I andQ branch amplitudes according to the digitized data.

At 403 the receiver calculates the sum-signal amplitude and sum-signalphase of the message element, based on the measured I and Q branchamplitudes. At 404, the receiver compares the calculated sum-signalamplitude and sum-signal phase to a set of predetermined amplitudelevels and phase levels of the sum-signal modulation scheme, and therebydemodulates the message. (Amplitude noise and phase noise are zero inthis example, but are treated in subsequent examples.)

The receiver uses quadrature branch separation for signal processingbecause it is much cheaper and easier to process the incoming signal astwo orthogonal components than to process the received waveform itself.Typically the receiver electronics include a high-frequency amplifierclose to the antenna, followed by two parallel subsystems thatseparately extract the I and Q branch signals. The receiver thenperforms frequency downconversion, filtering, and digitization (amongother tasks) by operating on the two branch signals separately. Thereceiver can then separate each subcarrier signal according tofrequency, and thereby determine the I and Q branch amplitudes of eachmessage element from the digitized data.

The receiver can then demodulate the message element using sum-signalamplitude and phase, instead of the quadrature amplitudes, to obtain theadvantageous noise margins. After measuring the I and Q branchamplitudes, the receiver can then calculate the sum-signal amplitude andsum-signal phase, using the formulas discussed above, for example. Theresulting sum-signal corresponds closely to the originally modulatedwaveform at the transmitter (aside from noise, excluded in this case).The receiver can then compare the sum-signal amplitude and phase to thepredetermined sum-signal amplitude and phase levels of the modulationscheme, as indicated by a demodulation reference proximate to themessage. For example, the receiver can select the closest match, foreach message element's sum-signal amplitude and phase, among thepredetermined sum-signal amplitude and phase levels of the modulationscheme. The receiver can thereby demodulate the message element whilepreserving the wide phase-noise margins provided by sum-signalmodulation and demodulation, while continuing to use the convenientbranch-separation receiver electronics for raw signal processing inquadrature.

The sum-signal modulation method differs from prior-art 16QAM in that(a) the message element is modulated, at the transmitter, according tosum-signal amplitudes and phases instead of I and Q branch amplitudes,and (b) the receiver converts the received I and Q branch amplitudesback to sum-signal amplitudes and phases before demodulation. Theintermediate steps (processing two quadrature signals in the receiver)are the same as with QAM. The average transmitter power is the same asthat of QAM since the maximum and minimum transmitted levels areunchanged. The message length and resource usage are the same as withQAM because they both provide the same number of bits per messageelement (that is, 4 bits in the examples shown). The difference,however, is that with sum-signal modulation, the phase noise margin hasbeen raised to 90 degrees (full width), instead of 37 degrees as in16QAM, thereby greatly reducing the incidence of phase faults. Inaddition, there are four equally-spaced amplitudes when modulatedaccording to the sum-signal waveform, as opposed to just three waveformamplitude levels, not equally spaced, with 16QAM. The extra sum-signalamplitude level, and their equal spacing, can provide higher throughputwhile avoiding amplitude faults, according to some embodiments.

For these reasons and those presented below, sum-signal modulation maybe offered as an advantageous noise-tolerant modulation scheme,especially for high-frequency wireless communication.

The following examples show how sum-signal modulation can mitigateamplitude and phase noise.

FIG. 5A is an exemplary embodiment of a sum-signal modulation table,according to some embodiments. As depicted in this non-limiting example,the sum-signal modulation table 501 is again shown, with states 502arranged according to sum-signal amplitude multiplexed with sum-signalphase. The amplitude separation 503 is uniform at one arbitrary unit andthe phase separation 504 is uniform at 90 degrees, for the case of a16-state modulation scheme. In the absence of noise, the receiver (aftersignal processing as described in the previous figure) determines asum-signal amplitude and phase for each message element, according tothis chart. The following figure shows how the received sum-signal canbe distorted by phase noise.

FIG. 5B is an exemplary embodiment of a sum-signal modulation tableincluding phase noise, according to some embodiments. As depicted inthis non-limiting example, the sum-signal states 512 are displaced by aphase rotation angle 511 to the new positions 513 shown as circles. Mostsources of phase noise (such as clock jitter, for example) affect thesystem time-base, not the individual modulation states separately.Therefore, all of the states are displaced by the same amount 511, andin the same direction, by phase noise in general. A message element,modulated according to the sum-signal scheme, is displaced by phasenoise by the same amount regardless of which modulation state is usedfor the particular message element. In contrast, the I and Q branchamplitudes of QAM are mixed together by phase noise, and the mixing isby different amounts at various regions of the constellation chart,greatly complicating phase noise mitigation.

Using sum-signal modulation, the receiver can mitigate phase noise bysimply subtracting the phase rotation angle from the received sum-signalphase of the received message element, regardless of the modulationstate. For example, the receiver can measure the phase rotation angle511 according to a demodulation reference proximate to the messageelement (preferably in the same symbol-time, and more preferably in thesame OFDM symbol, as the message element), and then subtract the phaserotation angle from the sum-signal phase, thereby obtaining a correctedsum-signal phase with the phase noise largely negated.

In another embodiment, the receiver can add the phase rotation angle tothe predetermined sum-signal phase levels of the modulation scheme, andthen compare the received sum-signal phases to the corrected sum-signalphase levels. It is immaterial whether the receiver adjusts the receivedphases or the calibration phase levels, so long as the phase noiseeffect is negated in the comparison.

FIG. 5C is an exemplary embodiment of a sum-signal modulation tableincluding amplitude noise, according to some embodiments. As depicted inthis non-limiting example, the sum-signal states 522 are displaced by anadditive amplitude adjustment 521 to the new positions 523 shown ascircles. Here the amplitude noise is assumed to be due to interferencefrom a signal which is synchronous, or almost synchronous, with thesum-signal, such as a transmission from a neighboring cell. The states522 are then increased in amplitude by the amount of amplitude noise ifthe states and the noise have the same overall phase, in which case thewave interference is called constructive interference. For othermodulation states that have the opposite phase, the interference isdestructive, in which case the sum-signal amplitude of the messageelement is reduced by the amplitude noise. The intermediate states,which are phased at 90 degrees relative to the amplitude noise, arelargely unaffected, aside from a slight interference phase shift whichis ignored in this example.

The receiver can measure the amplitude noise by measuring a demodulationreference proximate to the message element, compared to an expectedamplitude. Alternatively, the receiver can measure the unexpected signalreceived in a blank resource element, with no transmission. In eithercase, the receiver can add or subtract the amplitude adjustment to/fromthe received sum-signal amplitude, the sign depending on the relativephase between the interference and the sum-signal. If the interferenceand the sum-signal have the same phase, the effect is additive. If theyhave opposite phase, it is subtractive. In general, the correctedsum-signal amplitude equals the received sum-signal amplitude minus acorrection, wherein the correction equals the amplitude adjustment valuefrom the noise, times the cosine of the phase difference between thenoise and the sum-signal. In the example, the receiver can calculate anamplitude adjustment 521 as shown, and then add or subtract theamplitude adjustment 521 to or from the appropriate phase states 512according to the relative phase of the interference, thereby obtaining acorrected sum-signal amplitude with the amplitude noise largely negated.

According to the noise mitigation examples of the last two figures, thereceiver can detect, measure, and largely negate both phase noise andamplitude noise in message elements according to a proximatedemodulation reference, by simply adding or subtracting each noise typefrom the associated states of the received sum-signal waveform. As analternative, the receiver can leave the sum-signal amplitude and phaseunchanged, and adjust the predetermined amplitude and phase levelsinstead, and then compare the received sum-signal amplitude and phase tothose adjusted levels. The demodulation would be the same regardless ofwhether the received parameters or the predetermined levels are adjustedto mitigate the noise. Because the amplitude level adjustment depends onthe relative phase of the noise and the message sum-signal, it may besimpler to keep the predetermined levels constant and correct thereceived sum-signal amplitude and phase as described.

FIG. 5D is a flowchart showing an exemplary embodiment of a method tomitigate amplitude noise and phase noise in sum-signals, according tosome embodiments. As depicted in this non-limiting example, at 551 areceiver determines an amplitude adjustment value and a phase rotationangle, by determining how a demodulation reference deviates from thepredetermined amplitude and phase levels of the modulation scheme. At552 the receiver mitigates phase noise by subtracting the phase rotationangle from the received sum-signal phase of the message element. Thereceiver can also mitigate the sum-signal amplitude by adding orsubtracting the amplitude adjustment from the received sum-signalamplitudes, with the sign depending on the sum-signal phase, asdescribed. Thus the receiver can obtain a corrected message sum-signalamplitude and a corrected message sum-signal phase, for subsequentdemodulation with the noise mitigated.

In some embodiments, the phase noise mitigation is applied by adjustingthe predetermined phase levels of the modulation scheme according to thephase measurement of the most recent demodulation reference, and thendemodulating the received sum-signal phase according to thosephase-shifted predetermined phase levels. It is immaterial whether thephase mitigation is applied to the sum-signal phases as depicted, or tothe predetermined phase levels, since the resulting demodulation is thesame.

In some embodiments, the receiver can measure an amplitude of ademodulation reference and interpret this as an overall gain shift or achange in propagation attenuation, and then scale all of thepredetermined amplitude levels of the modulation scheme proportionally.However, such changes in overall amplitude are generally infrequent;most amplitude effects are due to transient coherent signals. Therefore,preferably, the receiver may apply such adjustments to the predeterminedamplitude levels only after determining that the amplitude effects aredue to a gain drift or propagation effect, and not due to episodicinterference.

In some embodiments, the demodulation reference, or the message itself,can include a blank resource element with no transmission. The receivercan determine the interference signal directly, by measuring thesum-signal amplitude and phase received during that blank resourceelement. The receiver can then use the sum-signal amplitude and phasevalues of the blank resource element to calculate the amplitudeadjustment, and can proceed with the amplitude mitigation as described.One example of a demodulation reference includes two resource elements;one with a predetermined transmission signal and the other with notransmission. Then the receiver can measure the resource elementmodulated according to a predetermined sum-signal amplitude andsum-signal phase, and thereby determine the phase rotation angleaccording to the received phase of the sum-signal in that transmittedresource element. The receiver can then measure noise signals in theblank resource element, which reveals the sum-signal amplitude andsum-signal phase coming from the interference alone. The demodulationreference can thereby enable both amplitude and phase noise mitigationat the same time, consuming just two resource elements.

FIG. 6 is a flowchart showing an exemplary embodiment of a procedure fortransmitting and receiving a message, while using sum-signaldemodulation to mitigate amplitude noise and phase noise, according tosome embodiments. As depicted in this non-limiting example, acommunication method for noise mitigation is described. At 601, atransmitter modulates a message of message elements, each messageelement modulated according to a modulation scheme, each state of themodulation scheme having multiplexed amplitude modulation and phasemodulation. Hence the transmitted waveform has a transmitted amplitudeand a transmitted phase according to the predetermined levels of themodulation scheme. In addition, as is normally the case, the transmittertransmits the message as an OFDM symbol that includes multiple messageelements, simultaneously transmitted at the same symbol-time, with eachmessage element occupying one subcarrier. Thus the transmitted waveformis the sum of the various subcarrier waves, each at a slightly differentfrequency.

At 602, a receiver receives the compound waveform including all themessage element signals overlapping, each message element with its ownsum-signal amplitude and sum-signal phase, at its own subcarrierfrequency. The receiver amplifies the antenna signal for further signalprocessing. At 603, the receiver separates the received waveform into Iand Q quadrature components. The receiver usually downshifts thefrequency coherently, and does other steps, before digitizing the twobranch components separately, for example using a pair of fastanalog-to-digital converters. The receiver can then measure the I and Qbranch amplitudes of the digitized signal in each subcarrier, forexample by digital filtering and other means, thereby determining thebranch amplitudes of the message element.

At 604, the receiver can convert the I and Q branch amplitudes to thecorresponding received sum-signal phase and sum-signal amplitude of eachmessage element. For example, the receiver can calculate the messagesum-signal amplitude as the square root of the sum of the I and Q branchamplitudes squared, and the sum-signal phase as the arctangent of the Qamplitude divided by the I amplitude.

Optionally, at 605, the receiver can mitigate noise by receiving ademodulation reference (which may be proximate to or simultaneous withthe message) and determining, from the sum-signal amplitude andsum-signal phase of the demodulation reference, a phase rotation angleand an amplitude adjustment value. For example, the receiver can measurethe I and Q branch amplitudes of the demodulation reference, calculatethe sum-signal amplitude and phase of the demodulation reference asdescribed above, and then compare the reference sum-signal amplitude andphase to a set of previously determined amplitude levels and phaselevels. For example, the receiver can determine the phase rotation angleby subtracting the predetermined sum-signal phase from the receivedsum-signal phase of the demodulation reference, and can also determinethe amplitude adjustment by subtracting the predetermined sum-signalamplitude from the received sum-signal amplitude of the demodulationreference. Then the receiver can then mitigate the noise by subtractingthe phase rotation angle from the sum-signal phase of the messageelement, obtaining a phase-corrected sum-signal phase, and can add orsubtract the amplitude adjustment from the received sum-signal amplitudeof the message element (depending on the sum-signal phase, asmentioned), thereby obtaining a noise-corrected sum-signal amplitude andphase.

At 606, the receiver can compare the corrected sum-signal amplitude andphase of the message element to a set of predetermined sum-signalamplitudes and a set of predetermined sum-signal phases, selecting theclosest phase and amplitude levels, and thereby determine whichmodulation state is encoded in the message element, and therebydemodulate the message element's content.

As a further option, at 607, the receiver can calculate a modulationquality for each message element according to the amplitude deviationand the phase deviation. For example, the receiver can calculate theamplitude deviation as the difference between the corrected sum-signalamplitude and the closest predetermined sum-signal amplitude level ofthe modulation scheme. Likewise, the phase deviation is the differencebetween the corrected sum-signal phase and the closest predeterminedphase level of the modulation scheme. If the message subsequently turnsout to be corrupted, the receiver can review the message elements,select one with the lowest modulation quality (that is, the largestamplitude and/or phase deviations), and attempt to repair the fault inthat message element, instead of automatically requesting aretransmission. For example, at 608 the receiver can select the messageelement with the lowest modulation quality, and alter the assignedamplitude or phase modulation state of the selected message element toeach of the other modulation states, testing each altered versionagainst an associated error-detection code. The receiver can therebydetermine whether one of the altered messages is correct. However, ifnone of those alterations is correct, the receiver can request aretransmission of the message.

The example assumes that the receiver separates the incoming waveforminto I and Q orthogonal branches for subsequent signal processing.However, in some embodiments, the receiver may be capable of signalprocessing the whole waveform as-received, instead of separating andprocessing the branches individually. In one embodiment, the receivercan process and digitize the whole waveform (optionally after frequencydownshifting). In another embodiment, the receiver can separate thebranches, but then generate a single combined digitized data stream bycombining the I and Q branch signals, instead of preparing two separatedigitized data streams. In each case, and other like embodiments, thereceiver can extract the message element according to its subcarrierfrequency from the combined data set, and can determine the sum-signalamplitude and sum-signal phase directly from the digitized data insteadof calculating the sum-signal parameters from the I and Q amplitudes.Many other signal-processing options are possible. It is immaterial howthe receiver processes the signals, so long as the receiver performs thedemodulation based on the sum-signal amplitude and phase.

FIG. 7A is an exemplary embodiment of a sum-signal modulation tableincluding various types of faults, according to some embodiments. Asdepicted in this non-limiting example, a receiver can diagnose problemsby determining the types of message faults received. For example, thereceiver can receive a corrupted message, as determined by disagreementwith an embedded error-detection code. The receiver may succeed inrepairing the corrupted first copy of the message, for example byaltering the message elements starting with the worst modulationquality, and thereby determine the corrected version. Alternatively, thereceiver can then request and receive a second copy, which may beuncorrupted. As a third alternative, if the copy is also corrupted, thereceiver may assemble a merged message by selecting, from thecorresponding message elements from the two copies, the message elementwith the highest modulation quality.

After determining the correct message, the receiver can then review themessage elements that differ between the corrupted and corrected copies,and can thereby determine how the faulted message element was distorted.For example, the receiver can determine whether the faulted messageelement (or elements) differs from the corrected version in thesum-signal phase or amplitude, or both. The receiver can also determinethe magnitude of the difference in phase or amplitude, to furthercategorize the fault type. Fault analysis can provide valuable feedbackto a network, especially regarding which other modulation scheme mayprovide better performance in the current noise environment.

The figure shows a sum-signal modulation table with sum-signal amplitudemultiplexed with sum-signal phase, and a variety of fault types by curvydashed arrows. A particular modulation state 700 is shown, along withvarious fault trajectories caused by noise, distorting the originalstate 700 to some other part of the modulation table. For example, thestate 700 can have an adjacent-phase fault 701 in which it is altered toanother state that differs by one phase level only. The state 700 can bealtered by an adjacent-amplitude fault 702 to another state differing byone amplitude level only. A non-adjacent fault 704 occurs when the state700 is displaced to another state that differs by more than oneamplitude level or more than one phase level or a combination ofamplitude and phase levels. A non-matching fault 703 occurs when thestate 700 is altered to a location (asterisk) that is so far from any ofthe predetermined modulation states that it cannot be demodulated.

An advantage of modulating with sum-signal parameters instead of QAMbranch amplitudes may be that, with sum-signal modulation the faultanalysis is clear and specific, whereas with QAM the amplitude noise andphase noise scramble the quadrature branch amplitudes in complex ways,complicating fault diagnosis.

FIG. 7B is a flowchart showing an exemplary embodiment of a method toselect a modulation table to mitigate various types of faults, accordingto some embodiments. As depicted in this non-limiting example, at 751 areceiver receives a corrupted message, then requests and receives anuncorrupted version of the same message. At 702, the receiver comparesthe message elements of the two versions, identifies one or more messageelements that differ between the two versions (therefore indicating thatthose message elements are faulted in the first version). The receiverthen determines the fault types based on the direction of thedisplacement (in phase or in amplitude) and the size of the displacement(adjacent or non-adjacent). Many other features are of interest, such aspossible clustering of the faults in a portion of the message, thetemporal distribution of faults by type to determine low-noise andhigh-noise intervals, frequency dependence of interference by type andmagnitude, among others. At 703, the receiver counts the number offaults of each type, accumulating a tally for each fault type. Thereceiver can also record the timing of faults or the rate ofaccumulation of fault types, and thereby identify specific times whenfaults may be driven by bursty interference, for example.

At 704, the receiver (or other entity such as a core network) cananalyze the accumulated fault data and determine which modulation schememay provide better results (such as fewer faults, higher net throughput,fewer dropped calls, or other performance metric). For example, ifadjacent-amplitude faults predominate, the receiver can suggestswitching to a different modulation scheme with fewer amplitude levelsand thus wider separation between the amplitude levels. Ifadjacent-phase faults are common, the receiver can switch to a schemewith fewer phase levels and thus a larger phase separation. If mostfaults are non-adjacent or non-matching, the receiver may determine thatthe occasional interference appears to be too strong for suchmitigations to be successful. In that case, switching to fewer amplitudeor phase levels would likely be futile. Instead, the receiver can do theopposite, by increasing the number of amplitude and/or phase levels. Thefaults may be due to occasional strong noise such as episodicinterference from another cell, in which case a better strategy may beto make the messages as short as possible, in time or bandwidth, so asto evade the noise episodes. In that case, the receiver can suggestusing a modulation scheme with more sum-signal amplitude and/or phaselevels, and hence a higher information content per message element,which therefore shortens the message overall. Alternatively, thereceiver can recommend increasing the transmission power (although thismay backfire if the interfering transmitter follows suit). As a furtheroption, the receiver can determine, from the timing or rate of messagefaults, when the interference is likely to re-appear, and may thentransmit the message between the instances of interference.

FIG. 8 is an exemplary embodiment of a sum-signal modulation tableconfigured to mitigate phase faults, according to some embodiments. Asdepicted in this non-limiting example, a sum-signal modulation scheme isshown with modulation states 801 surrounded by an acceptance zone 802,such that a received signal that has sum-signal amplitude and phasewithin one of the acceptance zones 802 is assigned “non-suspicious”while a modulation outside the acceptance zones 802 may be “suspicious”,although it may be demodulated according to the closest state anyway.There are two phase levels (P1, P2) separated by a phase separation 804(180 degrees in this case), multiplexed with eight amplitude levels(A1-A8) all separated by the same amplitude separation 803. Themodulation scheme is non-square in that the number Nphase of phaselevels is not equal to the number Namp of amplitude levels. Such asum-signal modulation scheme may be recommended by a receiver thatexperiences a high rate of phase faults with 16QAM or another modulationscheme. The wide phase separation 804 of the depicted chart may avoidmost phase faults. The number of states is 16, thereby keeping theinformation content the same (4 bits) in each message element.

An advantage of sum-signal modulation may be that it is readily adaptedfor asymmetric or non-square modulation tables which mitigate phasenoise natively. In contrast, QAM modulation schemes are generally notwell-suited to such asymmetric or non-square modulation schemes becausethe two branches are generally equivalent; hence, reducing either branchrelative to the other would likely provide no benefit. Another advantagemay be that the sum-signal amplitude and sum-signal phase are separatelymodulated, thereby providing additional versatility that enables thetransmitter and the receiver to adapt a non-square or asymmetric schemeto the noise environment.

FIG. 9 is a schematic showing an exemplary embodiment of a message withvarious types of faults, according to some embodiments. As depicted inthis non-limiting example, a faulted message 901 is shown as a series ofmodulated message elements, each message element having a sum-signalamplitude and a sum-signal phase (as in “A1-P1”). An unfaulted message902 is also shown. The faulted message 901 includes anadjacent-amplitude fault 903, an adjacent-phase fault 904, and anon-adjacent fault 905. The adjacent-amplitude fault 903 is a one-levelamplitude change, “A4-P4” being altered to “A3-P4”. The adjacent-phasefault 904 shows the phase modulation changed by one. The non-adjacentfault 905 has the amplitude changed by 3 levels.

The receiver can determine the message fault types by comparing themessage elements of faulted and unfaulted versions in a similar way, andthereby assist in selecting a more suitable modulation scheme, as shownin the next figure. In contrast, a fault in 16QAM generally alters bothI and Q branches in complex ways, and therefore is difficult for areceiver to determine the fault type, whether amplitude or phase fault.

FIG. 10 is a schematic showing an exemplary embodiment of a method toselect a modulation table based on types of faults observed, accordingto some embodiments. As depicted in this non-limiting example, astrategy for selecting a change in modulation can be based on the typeof faults detected. For example, responsive to adjacent-amplitudefaults, the receiver can suggest switching to a modulation scheme withfewer, and therefore more-spaced-apart, amplitude levels. Adjacent-phasefaults may prompt a reduction in the number of phase levels.Non-adjacent faults may require an increase in the number of sum-signalamplitude and sum-signal phase levels, in order to shorten the exposuretime of messages and thereby (attempt to) evade pulsatile stronginterference. If, however, the faults are uniformly spread throughoutthe modulation scheme, the best solution may be to increase thetransmission power, or alternatively to wait until the interferencesubsides. In persistent cases, a nice message from the victim corenetwork to the intruder core network may prompt a solution.

Due to the many options and variations disclosed herein, and otherversions derived therefrom by artisans after reading this disclosure, itwould be helpful for a wireless standards committee to establishconventions governing formats and implementation options for sum-signalmodulation as disclosed, so that future wireless users can enjoyphase-noise mitigation and amplitude-noise mitigation with eachcommunication.

The wireless embodiments of this disclosure may be aptly suited forcloud backup protection, according to some embodiments. Furthermore, thecloud backup can be provided cyber-security, such as blockchain, to lockor protect data, thereby preventing malevolent actors from makingchanges. The cyber-security may thereby avoid changes that, in someapplications, could result in hazards including lethal hazards, such asin applications related to traffic safety, electric grid management, lawenforcement, or national security.

In some embodiments, non-transitory computer-readable media may includeinstructions that, when executed by a computing environment, cause amethod to be performed, the method according to the principles disclosedherein. In some embodiments, the instructions (such as software orfirmware) may be upgradable or updatable, to provide additionalcapabilities and/or to fix errors and/or to remove securityvulnerabilities, among many other reasons for updating software. In someembodiments, the updates may be provided monthly, quarterly, annually,every 2 or 3 or 4 years, or upon other interval, or at the convenienceof the owner, for example. In some embodiments, the updates (especiallyupdates providing added capabilities) may be provided on a fee basis.The intent of the updates may be to cause the updated software toperform better than previously, and to thereby provide additional usersatisfaction.

The systems and methods may be fully implemented in any number ofcomputing devices. Typically, instructions are laid out on computerreadable media, generally non-transitory, and these instructions aresufficient to allow a processor in the computing device to implement themethod of the invention. The computer readable medium may be a harddrive or solid state storage having instructions that, when run, orsooner, are loaded into random access memory. Inputs to the application,e.g., from the plurality of users or from any one user, may be by anynumber of appropriate computer input devices. For example, users mayemploy vehicular controls, as well as a keyboard, mouse, touchscreen,joystick, trackpad, other pointing device, or any other such computerinput device to input data relevant to the calculations. Data may alsobe input by way of one or more sensors on the robot, an inserted memorychip, hard drive, flash drives, flash memory, optical media, magneticmedia, or any other type of file-storing medium. The outputs may bedelivered to a user by way of signals transmitted to robot steering andthrottle controls, a video graphics card or integrated graphics chipsetcoupled to a display that maybe seen by a user. Given this teaching, anynumber of other tangible outputs will also be understood to becontemplated by the invention. For example, outputs may be stored on amemory chip, hard drive, flash drives, flash memory, optical media,magnetic media, or any other type of output. It should also be notedthat the invention may be implemented on any number of different typesof computing devices, e.g., embedded systems and processors, personalcomputers, laptop computers, notebook computers, net book computers,handheld computers, personal digital assistants, mobile phones, smartphones, tablet computers, and also on devices specifically designed forthese purpose. In one implementation, a user of a smart phone orWi-Fi-connected device downloads a copy of the application to theirdevice from a server using a wireless Internet connection. Anappropriate authentication procedure and secure transaction process mayprovide for payment to be made to the seller. The application maydownload over the mobile connection, or over the Wi-Fi or other wirelessnetwork connection. The application may then be run by the user. Such anetworked system may provide a suitable computing environment for animplementation in which a plurality of users provide separate inputs tothe system and method.

It is to be understood that the foregoing description is not adefinition of the invention but is a description of one or morepreferred exemplary embodiments of the invention. The invention is notlimited to the particular embodiments(s) disclosed herein, but rather isdefined solely by the claims below. Furthermore, the statementscontained in the foregoing description relate to particular embodimentsand are not to be construed as limitations on the scope of the inventionor on the definition of terms used in the claims, except where a term orphrase is expressly defined above. Various other embodiments and variouschanges and modifications to the disclosed embodiment(s) will becomeapparent to those skilled in the art. For example, the specificcombination and order of steps is just one possibility, as the presentmethod may include a combination of steps that has fewer, greater, ordifferent steps than that shown here. All such other embodiments,changes, and modifications are intended to come within the scope of theappended claims.

As used in this specification and claims, the terms “for example”,“e.g.”, “for instance”, “such as”, and “like” and the terms“comprising”, “having”, “including”, and their other verb forms, whenused in conjunction with a listing of one or more components or otheritems, are each to be construed as open-ended, meaning that the listingis not to be considered as excluding other additional components oritems. Other terms are to be construed using their broadest reasonablemeaning unless they are used in a context that requires a differentinterpretation.

What is claimed is:
 1. A method for a wireless receiver to demodulate a message, the method comprising: a) receiving a message comprising message elements, each message element modulated according to a modulation scheme, the modulation scheme comprising amplitude modulation multiplexed with phase modulation, the amplitude modulation according to a first plurality of predetermined amplitude levels, and the phase modulation according to a second plurality of predetermined phase levels; b) for each message element, determining a message I-branch signal multiplexed with an orthogonal message Q-branch signal, and determining a message I-branch amplitude of the message I-branch signal, and determining a message Q-branch amplitude of the message Q-branch signal; c) for each message element, calculating, according to the message I-branch amplitude and the message Q-branch amplitude, a message sum-signal amplitude and a message sum-signal phase; and d) for each message element, selecting a closest amplitude level, of the first plurality of predetermined amplitude levels, to the message sum-signal amplitude, and selecting a closest phase level, of the second plurality of predetermined phase levels, to the message sum-signal phase.
 2. The method of claim 1, wherein the message is configured according to 5G or 6G technology.
 3. The method of claim 1, further comprising: a) receiving a demodulation reference modulated, by a transmitter, according to a particular amplitude level of the first plurality and a particular phase level of the second plurality; b) determining a reference I-branch amplitude and a reference Q-branch amplitude of the demodulation reference as received; c) determining, according to the reference I-branch amplitude and the reference Q-branch amplitude, a reference sum-signal amplitude and a reference sum-signal phase.
 4. The method of claim 3, further comprising: a) determining, according to the reference sum-signal phase and the particular phase level, a phase rotation angle; and b) for a particular message element of the message, determining a corrected sum-signal phase by subtracting the phase rotation angle from the message sum-signal phase.
 5. The method of claim 4, further comprising: a) determining, according to the reference sum-signal amplitude and the particular amplitude level, an amplitude adjustment; and b) for the particular message element, determining a corrected sum-signal amplitude by adding or subtracting the amplitude adjustment to or from the message sum-signal amplitude.
 6. The method of claim 5, further comprising: a) for the particular message element, selecting a closest amplitude level, of the first plurality of predetermined amplitude levels, to the corrected sum-signal amplitude, and selecting a closest phase level, of the second plurality of predetermined phase levels, to the corrected sum-signal phase.
 7. The method of claim 6, further comprising: a) for the particular message element, calculating a modulation quality according to an amplitude deviation and a phase deviation, wherein: b) the amplitude deviation comprises a difference between the corrected sum-signal amplitude and the closest predetermined amplitude level; and c) the phase deviation comprises a difference between the corrected sum-signal phase and the closest predetermined phase level.
 8. The method of claim 3, further comprising: a) correcting each predetermined amplitude level of the first plurality according to the reference sum-signal amplitude; b) correcting each predetermined phase level of the second plurality according to the reference sum-signal phase; c) for each message element, selecting a closest amplitude level, of the first plurality of the corrected predetermined amplitude levels, to the message sum-signal amplitude, and selecting a closest phase level, of the second plurality of corrected predetermined phase levels, to the message sum-signal phase.
 9. The method of claim 1, wherein: a) the predetermined amplitude levels of the first plurality are equally spaced apart; and b) the predetermined phase levels of the second plurality are equally spaced apart.
 10. The method of claim 9, wherein: a) the predetermined amplitude levels of the first plurality comprise integer Namp predetermined amplitude levels; b) the predetermined phase levels of the second plurality comprise integer Nphase predetermined phase levels; and c) Namp is different from Nphase.
 11. Non-transitory computer-readable media in a wireless receiver, the media containing instructions that when implemented in a computing environment cause a method to be performed, the method comprising: a) receiving a first message comprising message elements, wherein each message element is amplitude modulated and phase modulated according to a first modulation scheme; b) determining, according to an error-detection code associated with the first message, that the first message is corrupted; c) receiving a second message, and determining, according to a second error-detection code associated with the second message, that the second message is not corrupted; d) determining, for each message element of the first and second messages, a raw-signal amplitude and a raw-signal phase; e) for each message element, comparing the raw-signal amplitude of the first message to the raw-signal amplitude of the second message, and comparing the raw-signal phase of the first message to the raw-signal phase of the second message; and f) determining, according to the comparing steps, which message elements of the first message are faulted.
 12. The media of claim 11, wherein: a) the first modulation scheme comprises a first plurality of predetermined amplitude levels and a second plurality of predetermined phase levels; and b) each message element, of the first and second messages, is amplitude modulated according to one of the predetermined amplitude levels, and phase modulated according to one of the predetermined phase levels.
 13. The media of claim 12, the method further comprising: a) for each message element of the first and second messages, determining a received amplitude and a received phase; b) for each message element of the first and second messages, assigning, to the message element, the predetermined amplitude level of the first plurality that is closest to the received amplitude; and c) for each message element of the first and second messages, assigning, to the message element, the predetermined phase level of the second plurality that is closest to the received phase; and d) determining that a particular message element of the first message is faulted when either: i) the assigned amplitude levels of the corresponding message elements of the first and second messages differ; or ii) the assigned phase levels of the corresponding message elements of the first and second messages differ.
 14. The media of claim 13, the method further comprising: a) determining a rate or number of adjacent-amplitude faults wherein the corresponding message elements differ by a single amplitude level only; b) determining a rate or number of adjacent-phase faults wherein the corresponding message elements differ by a single phase level only; c) determining a rate or number of non-adjacent faults wherein the corresponding message elements differ by at least one of: i) more than one phase level; or ii) more than one amplitude level; or iii) one phase level and one amplitude level.
 15. The media of claim 14, the method further comprising: a) when the rate or number of adjacent-amplitude faults exceeds a second threshold, transmitting a message suggesting a second modulating scheme having fewer amplitude levels than the first modulation scheme; and b) when the rate or number of adjacent-phase faults exceeds a third threshold, transmitting a message suggesting a third modulating scheme having fewer phase levels than the first modulation scheme.
 16. The media of claim 14, the method further comprising: a) when the rate or number of non-adjacent faults exceeds a fourth threshold, transmitting a message suggesting a fourth modulation scheme having more amplitude levels than the first modulation scheme and more phase levels than the first modulation scheme.
 17. A receiver in a wireless network, the receiver configured to: a) receive a particular message element of a wireless message, the particular message element comprising a raw signal, the raw signal modulated according to a modulation scheme, the modulation scheme comprising amplitude modulation multiplexed with phase modulation; b) separate the raw signal into an I-branch signal and an orthogonal Q-branch signal; c) measure an I-branch amplitude of the I-branch signal and a Q-branch amplitude of the Q-branch signal; d) calculate, according to the I-branch amplitude and the Q-branch amplitude, a received sum-signal amplitude and a received sum-signal phase; and e) demodulate the particular message element according to the received sum-signal amplitude and the received sum-signal phase.
 18. The receiver of claim 17, further configured to: a) receive, proximate to the message element, a demodulation reference; b) determine, according to the demodulation reference, a phase rotation angle; and c) determine a corrected sum-signal phase by subtracting the phase rotation angle from the received sum-signal phase.
 19. The receiver of claim 18, further configured to: a) determine, according to the demodulation reference, an amplitude adjustment value; b) determine a corrected sum-signal amplitude by adding or subtracting the amplitude adjustment value, or a portion thereof, to or from the received sum-signal amplitude.
 20. The receiver of claim 19, further configured to: a) demodulate the particular message element by i) comparing the corrected sum-signal amplitude to a first plurality of predetermined amplitude levels and selecting which of the predetermined amplitude levels is closest to the corrected sum-signal amplitude; and ii) comparing the corrected sum-signal phase to a second plurality of predetermined phase levels and selecting which of the predetermined phase levels is closest to the corrected sum-signal phase. 